Immune suppression via IL-4/IL-10-secreting T cells: A nontoxic property of anti-HIV agent Trichosanthin

Trichosanthin-derived peptide Tk-PQ attenuates immune rejection in mouse tracheal allotransplant model by suppressing PI3K-Akt and inducing type II immune polarization

Obliterative bronchiolitis (OB) is one of the main complications affecting long-term survival of post-lung transplantation patients. In this study, we evaluated the efficacy of Tk-PQ (a peptide derived from trichosanthin) in alleviating OB in a mouse ectopic tracheal transplant model. We found that post-transplantation treatment of Tk-PQ significant ameliorated OB symptoms including luminal occlusion, epithelial cells loss and fibrosis in the allograft. In addition, Tk-PQ promoted immune suppressive environment by inducing Th2 polarization and increasing Treg population which in turn led to elevated levels of anti-inflammatory cytokines IL-4, IL-10, IL-33 and decreased levels of pro-inflammatory IL-1β. Mechanistically, we used transcriptome analysis of splenic T cells from allografted mice to show that Tk-PQ treatment down-regulated the PI3K-Akt signaling pathway. Indeed, the immune suppression phenotypes of Tk-PQ was recapitulated by a PI3K inhibitor LY294002. Taken together, Tk-PQ regulates post-transplantation immuno-rejection by modulating the balance of T cell response via the PI3K-Akt pathway, making it a promising peptide based immune rejection suppressant for patients receiving allotransplant.

Structural and Functional Investigation and Pharmacological Mechanism of Trichosanthin, a Type 1 Ribosome-Inactivating Protein

Trichosanthin (TCS) is an RNA N-glycosidase that depurinates adenine-4324 in the conserved α-sarcin/ricin loop (α-SRL) of rat 28 S ribosomal RNA (rRNA). TCS has only one chain, and is classified as type 1 ribosome-inactivating protein (RIP). Our structural studies revealed that TCS consists of two domains, with five conserved catalytic residues Tyr70, Tyr111, Glu160, Arg163 and Phe192 at the active cleft formed between them. We also found that the structural requirements of TCS to interact with the ribosomal stalk protein P2 C-terminal tail. The structural analyses suggest TCS attacks ribosomes by first binding to the C-terminal domain of ribosomal P protein. TCS exhibits a broad spectrum of biological and pharmacological activities including anti-tumor, anti-virus, and immune regulatory activities. This review summarizes an updated knowledge in the structural and functional studies and the mechanism of its multiple pharmacological effects.

Peptide Tk-PQ induces immunosuppression in skin allogeneic transplantation via increasing Foxp3+ Treg and impeding nuclear translocation of NF-κB

Solid organ transplantation is used as the last resort for patients with end-stage disease, but allograft rejection is an unsolved problem. Here, we showed that Tk-PQ, a peptide derived from trichosanthin, had an immune-suppressive effect without obvious cytotoxicity in vitro and in a mouse skin allo-transplantation model. In vitro, treatment of Tk-PQ administrated type 2 T helper cell (Th2)/regulatory T-cell (Treg) cytokines, and increased the ratio of CD4⁺CD25⁺Foxp3⁺ Treg by repressing the PI3K/mTOR pathway. In addition, Tk-PQ decreased NF-κB activation to downregulate pro-inflammatory cytokines. Tk-PQ treatment in the mouse skin transplantation model also caused the similar molecular and cellular phenotypes. Furthermore, Tk-PQ enhanced the suppressive function of Treg by increasing Foxp3 expression, and substantially improved allograft survival. These finding demonstrate that Tk-PQ has the potential to be used in clinical allogeneic transplantation.

Chinese Medicine Protein and Peptide in Gene and Cell Therapy

The success of gene and cell therapy in clinic during the past two decades as well as our expanding ability to manipulate these biomaterials are leading to new therapeutic options for a wide range of inherited and acquired diseases. Combining conventional therapies with this emerging field is a promising strategy to treat those previously-thought untreatable diseases. Traditional Chinese medicine (TCM) has evolved for thousands of years in China and still plays an important role in human health. As part of the active ingredients of TCM, proteins and peptides have attracted long-term enthusiasm of researchers. More recently, they have been utilized in gene and cell therapy, resulting in promising novel strategies to treat both cancer and non-cancer diseases. This manuscript presents a critical review on this field, accompanied with perspectives on the challenges and new directions for future research in this emerging frontier.

A peptide tetramer Tk-tPN induces tolerance of cardiac allografting by conversion of type 1 to type 2 immune responses via the Toll-like receptor 2 signal-promoted activation of the MCP1 gene

The plant protein trichosanthin (Tk) and its derived peptide tetramer Tk-tPN have been shown to stimulate the type 2 immune responses for treating autoimmune disease. This work explores the possibility of using Tk-tPN as a non-toxic immunosuppressant to induce transplantation tolerance using the mechanisms by which T-cell-mediated immune responses are transferred from type 1 to type 2 through innate immunity-related pathways. Immunocytes and cytokine secretions involved in the mouse cardiac allografting model with Tk-tPN treatment were characterized. Identification of critical genes and analysis of their functions through Toll-like receptor (TLR) -initiated signalling and the possible epigenetic changes were performed. Mean survival times of the cardiac allografts were delayed from 7.7 ± 0.3 days (control) to 22.7 ± 3.9 days (P < 0.01) or 79.1 ± 19.2 days (P < 0.0001) when Tk-tPN was introduced into the recipients alone or together with rapamycin, respectively. The grafting tolerance was donor-specific. The secretion pattern of the type 1 cytokine/transcription factor (IL-2(+) IFN-γ(+) T-bet(+)), which is responsible for the acute graft rejection, was shifted to the type 2 factor (IL-4(+) IL-10(+) Gata3+), together with a selective expansion of the IL-4/IL-10-producing CD8+ CD28- regulatory T-cell subset. A TLR2-initiated high expression of chemokine gene MCP1 was detectable simultaneously. Epigenetically Tk/Tk-tPN could also acetylate the histone H3K9 of MCP1 promoter to skew the immunity towards T helper type 2 responses. Tk/Tk-tPN is therefore capable of down-regulating the type 1 response-dominant rejection of cardiac allografts by evoking type 2 immunity through the activation of a TLR2-initiated signalling pathway and MCP1 gene to expand the IL-4/IL-10-secreting CD8+ CD28- regulatory T cells. Tk-tPN could be a promising novel immunosuppressant to induce tolerance in allotransplantation.

Modeling and analysis of Schistosoma Argonaute protein molecular spatial conformation

OBJECTIVE

To analyze the amino acid sequence composition, secondary structure, the spatial conformation of its domain and other characteristics of Argonaute protein.

METHODS

Bioinformatics tools and the internet server were used. Firstly, the amino acid sequence composition features of the Argonaute protein were analyzed, and the phylogenetic tree was constructed. Secondly, Argonaute protein's distribution of secondary structure and its physicochemical properties were predicted. Lastly, the protein functional expression form of the domain group was established through the Phyre-based analysis on the spatial conformation of Argonaute protein domains.

RESULTS

593 amino acids were encoded by Argonaute protein, the phylogenetic tree was constructed, and Argonaute protein's distribution of secondary structure and its physicochemical properties were obtained through analysis. In addition, the functional expression form which comprised the N-terminal PAZ domain and C-terminal Piwi domain for the Argonaute protein was obtained with Phyre.

CONCLUSIONS

The information relationship between the structure and function of the Argonaute protein can be initially established with bioinformatics tools and the internet server, and this provides the theoretical basis for further clarifying the function of Schistosoma Argonaute protein.

Bioactive proteins and peptides isolated from Chinese medicines with pharmaceutical potential

Some protein pharmaceuticals from Chinese medicine have been developed to treat cardiovascular diseases, genetic diseases, and cancer. Bioactive proteins with various pharmacological properties have been successfully isolated from animals such as Hirudo medicinalis (medicinal leech), Eisenia fetida (earthworm), and Mesobuthus martensii (Chinese scorpion), and from herbal medicines derived from species such as Cordyceps militaris, Ganoderma, Momordica cochinchinensis, Viscum album, Poria cocos, Senna obtusifolia, Panax notoginseng, Smilax glabra, Ginkgo biloba, Dioscorea batatas, and Trichosanthes kirilowii. This article reviews the isolation methods, molecular characteristics, bioactivities, pharmacological properties, and potential uses of bioactive proteins originating from these Chinese medicines.

A Trichosanthin-derived peptide suppresses type 1 immune responses by TLR2-dependent activation of CD8(+)CD28(-) Tregs

A group of 15-aa-long Trichosanthin-derived peptides was synthesized and screened based on their differential abilities to induce low-responsiveness in mouse strains with high and low susceptibility. One of them was conjugated to form a homo-tetramer Tk-tPN. At concentrations of 0.1-50 μg/ml, Tk-tPN activated CD8(+)CD28(-) Tregs in vitro to induce immune suppression as effectively as the native Trichosanthin but did not exhibit cytotoxicity. In EAE mice which were pre-treated with Tk-tPN or Tk-tPN-activated CD8(+) T cells, a marked attenuation of clinical scores was recorded together with an expansion of the CD8(+)CD28(-) Treg from 2.2% to 36.1% in vivo. A pull-down assay and signal transduction analyses indicated that the ability of Tk-tPN to convert the CD8(+)CD28(-) Treg-related cytokine secretion pattern from type 1 to type 2 depends on the TLR2-initiated signaling in macrophages. The high production of IL-4/IL-10 by the Tk-tPN-activated CD8(+)CD28(-) Treg suggests the value of using Tk-tPN as a therapeutic reagent for Th1-dominant immunological diseases.

Suppression of T-cell activation in vitro and in vivo by cordycepin from Cordyceps militaris

BACKGROUND

In addition to achieving a balance between the positive (controlling rejection) and the negative (infection and malignancy) aspects of drug-induced immunodeficiency, new immunosuppressive combinations must address the issue of nonimmune drug toxicity that may be dose limiting. Cordycepin is a type of adenosine analog extracted from Cordyceps militaris. In the present study, we investigated its immunosuppressive effect on T cell both in vitro and in vivo.

METHODS

We evaluated the effects of cordycepin on concanavalin A-induced production of immune mediators in mouse splenocyte by enzyme-linked immunosorbent assay and flow cytometry. Furthermore, using Western blotting, we studied signal transduction mechanisms to determine how cordycepin inhibited T-cell activation in purified mouse T lymphocytes. To confirm the immunosuppressive activity of cordycepin in vivo, we induced the T cell-mediated delayed-type hypersensitivity reaction in a 2,4-dinitro-1-fluorobenzene-induced mouse model.

RESULTS

The in vitro results showed that cordycepin markedly suppressed concanavalin A-induced splenocyte proliferation, Th1 and Th2 cytokine production, and the ratio of CD4(+)-to-CD8(+) T cells. The administration of cordycepin in vivo markedly suppressed the T cell-mediated delayed-type hypersensitivity reaction. The data revealed that cordycepin effectively shocked the nuclear factor kappa B and nuclear factor of activated T cells 2 signal transduction pathways but had no effect on the mitogen activated protein kinase signal transduction pathway.

CONCLUSIONS

These observations indicated that cordycepin has a potential role in downregulating the immune system and could be developed as a useful immunosuppressive agent for treating undesired immune responses.

Trichosanthin enhances anti-tumor immune response in a murine Lewis lung cancer model by boosting the interaction between TSLC1 and CRTAM

Trichosanthin (TCS), extracted from the Chinese medicinal herb Trichosanthes kirilowi, has shown promise for the inhibition of tumor growth. However, its immunomodulatory effect on tumor-host interaction remains unknown. In this study, we focused on the effect of TCS on murine anti-tumor immune response in the 3LL Lewis lung carcinoma tumor model and explored the possible molecular pathways involved. In addition to inhibiting cell proliferation and inducing apoptosis in the 3LL tumor, TCS retarded tumor growth and prolonged mouse survival more significantly in C57BL/6 immunocompetent mice than in nude mice. This reflected the fact that the host immune system was involved in tumor eradication. Using FACS analysis, we found that TCS increased the percentage of effector T cells, particularly Interferon-gamma (IFN-γ) producing CD4(+) and CD8(+) T cells from tumor-bearing mice. TCS also promoted the vigorous proliferation of antigen-specific effector T cells, markedly increased Th1 cytokine secretion and elicited more memory T cells in tumor-bearing mice, consequently enhancing the anti-tumor response and inducing immune protection. Furthermore, we found that TCS upregulated the expression of tumor suppressor in lung cancer 1 (TSLC1) in 3LL tumor cells and the expression of its ligand, class I-restricted T cell-associated molecule (CRTAM), in effector T cells. Blocking TSLC1 expression with small interfering RNA (siRNA) significantly eliminated the effects of TCS on the proliferation and cytokine secretion of effector T cells, suggesting that TCS enhances anti-tumor immune response at least partially by boosting the interaction between TSLC1 and CRTAM. Collectively, our data demonstrate that TCS not only affects tumor cells directly, but also enhances anti-tumor immunity via the interaction between TSLC1 and CRTAM. These findings may lead to the development of a novel approach for tumor regression.

A role for trichosanthin in the expansion of CD4CD25 regulatory T cells

CD4(+)CD25(+) regulatory T cells (Tregs) are critical for the peripheral immune tolerance. Understanding the signals for the generation of Tregs is important for the clinical immunotherapy, but only limited progress has been made on obtaining enough peripheral Tregs. The aim of this study was to evaluate the role of trichosanthin (Tk) extracted from Chinese medicinal herb Trichosanthes kirilowi on the function of Tregs in vitro and in vivo. We reported here that Tk is needed for the expansion of freshly isolated CD4(+)CD25(+)Tregs (nTregs) into Tk-expanded CD4(+)CD25(+)Tregs (Tk-Tregs) through up-regulating CD25 and Foxp3 expression. The dose-response analyses indicated that 100 ng/ml Tk was the most appropriate dose. The result of real-time PCR showed that Tk-Tregs expressed 1.5-fold higher levels of Foxp3 than those observed in nTregs. Tk-Tregs markedly suppressed activation of effector T cells at a suppressor/responder ratio of 1:1, 1:2, 1:4, 1:8 or 1:16, and their effect was dose dependent. Moreover, Tk-Tregs secreted more immunosuppressive cytokines interleukin (IL)-10 and transforming growth factor (TGF)-beta1 after stimulating with antigen and antigen-presenting cells (APC). Transwell experiments showed that not only cell-to-cell contact but also soluble cytokines were involved in suppressive mechanism of Tk-Tregs. And Tk-Tregs were more efficient in suppressing CD25(-)T cell response to specific antigen than to irrelative antigen. Most importantly, it was revealed for the first time that Tk-Tregs could prolong the survival duration of mice with acute graft-versus-host disease (aGVHD). In conclusion, the study suggests a possible therapeutic potential of Tk-Tregs for clinical treatment on aGVHD.

Trichosanthin, an extract of Trichosanthes kirilowii, effectively prevents acute rejection of major histocompatibility complex-mismatched mouse skin allograft

Trichosanthin is an active component extracted from the root tuber of the Chinese medicinal herb Trichosanthes kirilowii. Trichosanthin has abortifacient, anti-tumor, anti-HIV, and immunoregulatory functions. In the current study, we explored its potential effect on allograft rejection in a murine skin transplantation model across a fully mismatched major histocompatibility complex. It was found that treatment of recipient mice with trichosanthin (0.25 or 1 mg/kg, IP) significantly delayed allograft rejection. T cells that originated from recipients treated with trichosanthin were restimulated with donor-specific splenocytes showed a significantly reduced response compared with that of control recipients. In line with these results, the mRNA levels for interleukin (IL)-2 and interferon-gamma were decreased and the levels of IL-4 and IL-10 were increased in splenic T cells originating from trichosanthin-treated recipients. These results indicated that trichosanthin may have potential therapeutic value for transplantation rejection and other inflammatory diseases.

Up-regulation of IL-10 expression in dendritic cells is involved in Trichosanthin-induced immunosuppression

We report here that Trichosanthin (Tk), a primary active component isolated from a Chinese traditional medicinal herb, Trichosanthes kirilowii, potently inhibits lymphocyte proliferative response in vitro. We found that Tk treatment increased production of the interleukins IL-4 and IL-10, while production of IL-2 and interferon-gamma (IFN-gamma) decreased in the allogeneic antigen-induced immune response. Moreover, up-regulation of IL-10 and IL-4 contributed to the inhibitory activities of Tk. Tk induced immunosuppression through an antigen presenting cell dependent way. Dendritic cells (DCs) are the most potent of the antigen presenting cells, which play a critical role in initiation and regulation of immune responses. We found that Tk could stimulate bone marrow-derived dendritic cells (BMDC) to express IL-10. In addition, pre-exposure of BMDC to Tk produced increased levels of IL-10, but decreased levels of IL-12, following subsequent lipopolysaccharide (LPS) stimulation. Using BMDC obtained from IL-10 deficient mice, we provided evidence that it was IL-10 derived from DCs that initiated the Tk-induced immunosuppression. Furthermore, we found that Tk activated c-Jun N-terminal kinase (JNK) of BMDC and that JNK and p38 mitogen-activated protein kinase (MAPK) activations were associated with Tk-induced IL-10 up-regulation. These data suggest that Tk acts on the function of DCs to change the ratio of IL-10 to IL-12 production and, thus, predominantly inhibits Th1 responses.